Fundamental aspects of the freezing of cells, with emphasis on mammalian ova and embryos. (Aspectos fundamentales de la congelacion de celulas, especialmente ovulos y embriones de mamiferos
For most cells there exists an optimum cooling rate. Both supraoptimal rates and suboptimal rates can be very damaging. The optimal rate varies enormously from less than or equal to 1/sup 0/C/min for mammalian preimplantation embryos to greater than or equal to 800/sup 0/C/min for the human red cell. Death at supraoptimal rates is the result of the formation of intracellular ice and its recrystallization during warming. Intracellular ice occurs when cells are cooled too rapidly to allow them to equilibrate by the osmotic withdrawal of intracellular water. The definition of too rapid depends chiefly on the size of the cell and its permeability to water. Death at suboptimal rates is a consequence of the major alterations in aqueous solutions produced by ice formation. The chief effects are a major reduction in the fraction of the solution remaining unfrozen at a given temperature and a major increase in the solute concentration of that fraction. Presumably, slow freezing injury is a consequence of one or both of these solution effects. The introduction of molar concentrations of protective solutes (additives) greatly reduces both the fraction frozen and the concentration of electrolytes in the unfrozen channels and in the cell interior. Usually, freezing either kills cells outright or it yields survivors that retain full capacity to function. Although there is the possibility that in some cases survivors may in fact be impaired genetically, all evidence indicates that genetic damage does not occur. But there are clear examples in which freezing does induce nonlethal physiological damage. Particularly striking examples are found in certain mammalian sperm.
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5654915
- Country of Publication:
- United States
- Language:
- English
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